Subscribers in telecommunications networks desire to know the identity of the person who is calling them, i.e., the calling party's identification, commonly referred to as caller ID (CID). One of the first forms of caller identification was made available to users of public switched telephone networks (PSTN), also known as plain old telephone service (POTS), and it displayed to the called party the calling party's telephone number. Although known as caller ID, it is more precisely known as calling number identification (CNID), since it displays the identity of the number used by the caller, rather than the actual identify of the caller. Nevertheless, since the correlation between the caller and the calling party number used by the caller is high, identifying the calling party number usually suffices to identify the calling party.
A later form of caller identification was developed, which, instead of displaying the calling party's number, displayed a name that was associated with that number. This form of caller identification is known as calling name identification, or “CNAM”. Like CNID, CNAM too was originally developed on PSTN networks, which use the signaling system 7 (SS7) protocol for call setup, takedown, and other call-related functions.
With the advent of packet networks, such as the Internet, the distinction between traditional telecommunication networks, such as PSTN networks using SS7, and data networks, such as the Internet, became increasingly blurred as telephone calls were routed through packet networks (e.g., voice-over IP, or VoIP), and Internet services were made available to mobile telephone users (e.g., web browsing on a smart phone). The session initiation protocol (SIP) became increasingly popular due to its ability to manage multimedia streams between endpoints, e.g., allowing a cell phone user to download and play music from a internet host, allowing computer users to hold videoconferences over the Internet, and so on.
One problem, however, is that since SIP and SS7 were developed separately and on incompatible network types (packet switched and circuit-switched, respectively), some services available on PSTN networks are not available on SIP networks, and vice versa. One such service is CNAM, which was originally developed for SS7 networks. Thus, the CNAM databases are typically located in SS7 networks, and respond to queries using SS7 protocols. As a result, the existing SS7 infrastructure that provides the CNAM service for mapping a PSTN telephone number to a calling name is not accessible to SIP nodes which communicate using the SIP protocol. In other words, SIP nodes can't perform CNAM queries into the SS7 domain using the SIP protocol.
There have been two conventional solutions to this problem. The first solution is to upgrade the CNAM databases in the SS7 domain to handle queries from SIP nodes. This conceptually moves the SS7-based CNAM databases into the SIP domain. The second solution is to upgrade all SIP nodes to perform CNAM queries using SS7 protocols. This conceptually moves the SIP nodes into the SS7 domain. Both solutions are very expensive, requiring additional software and hardware for every SIP node in the packet-switched network, every CNAM node in the circuit-switched network, or some combination of the two.
Accordingly, there exists a need for an inexpensive way to pass CNAM information associated with a call from an SS7 domain into a SIP domain. Specifically, there exists a need for communicating calling name information between signaling system 7 (SS7) and non-SS7 networks.